Abstract

The southeastern United States (US) coastal plain is a unique physiographic region with extensive connections between land and water, and these connections fuel transformations and transport of carbon and nutrients to productive coastal ecosystems. Urbanization, or an increase in the extent of urban area, is occurring rapidly in the southeastern US coastal plain, and although stormwater runoff from urban areas can have negative effects on the ecology of downstream waters, research on this topic in the coastal plain is limited. Engineering approaches characterized as stormwater control measures (SCMs) have been widely implemented in the coastal plain to mitigate negative ecological effects of stormwater runoff without information regarding the long-term impact of SCMs or how they process nutrients. This dissertation characterized the effects of urbanization on coastal plain stream nutrient and carbon export and characterized the efficacy and process-level function of SCMs. Chapter 1 is a review and synthesis that highlights critical gaps related to nitrogen cycling within SCMs. Chapter 2 analyzes flow-through sediment core incubations to measure seasonal nitrogen cycling in coastal stormwater ponds. Chapters 3 and 4 use a years-long streamflow and water quality dataset to analyze the impacts of urbanization on coastal plain stream carbon and nitrogen export. Results from this research show that stormwater ponds often act as temporary sinks for stormwater-derived nutrients or as transformers of nitrogen from inorganic to organic forms, especially during periods of high water temperatures. Results indicated that the volume of stormflow and the amount of nitrogen and carbon exported from coastal streams during storms increased with development. Naturally high concentrations of organic nitrogen and dissolved organic carbon decreased with urbanization, with differences in nitrogen and carbon quality indicating shifts towards more labile anthropogenic sources. This research provides actionable information that managers can use to better mitigate the biogeochemical and ecological effects of urbanization on streams in the southeastern US coastal plain.

About this resource

This is a Ph.D. dissertation written by Adam C. Gold, an advisee of Rachel Noble at the University of North Carolina at Chapel Hill. Some of this research was conducted as part of a 2016 - 2020 collaborative research project, which involved a partnership with the North Carolina National Estuarine Research Reserve.